n=int(input())
c=list(input())

cntr=c.count('R')

cnt=0
for i in range(0,cntr):
  if c[i]=='W':
    cnt+=1

print(cnt) n=int(input()) n int(input()) int input() input c=list(input()) c list(input()) list input() input cntr=c.count('R') cntr c.count('R') c.count c count 'R' cnt=0 cnt 0 for i in range(0,cntr):
  if c[i]=='W':
    cnt+=1 i range(0,cntr) range 0 cntr if c[i]=='W':
    cnt+=1 c[i]=='W' c[i] c i 'W' cnt+=1 cnt 1 print(cnt) print cnt cntr=c.count('R') c.count('R') cntr cnt=0 0 cnt c=list(input()) list(input()) c n=int(input()) int(input()) n cnt+=1 1 cnt
n=int(input())
c=list(input())

cntr=c.count('R')

cnt=0
for i in range(0,cntr):
  if c[i]=='W':
    cnt+=1

print(cnt)